Petrogenesis of the olivine cumulate outcrop Issole – The missing link between the Séítah and Máaz formations in Jezero crater, Mars

Creators: Hernández-Montenegro, Juan David¹; Kizovski, Tanya V.²; Treiman, Allan H.³; Li, An Y.⁴; Asimow, Paul D.¹; Schmidt, Mariek E.²; Liu, Yang⁵; Labrie, Josh²; Knight, Abigail L.⁶; Tice, Michael M.⁷; Klevang, David A.⁸; VanBommel, Scott⁶; Wade, Lawrence A.⁵; Hurowitz, Joel A.⁹; Brown, Adrian J.¹⁰; Cable, Morgan L.⁵; Allwood, Abigail C.⁵; PIXL Team

1. California Institute of Technology
2. Brock University
3. Lunar and Planetary Institute
4. University of Washington
5. Jet Propulsion Lab
6. Washington University in St. Louis
7. Texas A&M University
8. Technical University of Denmark
9. Stony Brook University
10. Plancius Research

Abstract

Two lithologic units have been mapped and studied on the floor of Jezero crater, Mars: Séítah, which consists of layered olivine-rich cumulates, and Máaz, a series of basaltic to trachyandesitic lava flows. While Séítah and Máaz are close in proximity and stratigraphy, their potential geologic and petrological relationship remains unclear. Here, we present observations from the Planetary Instrument for X-ray Lithochemistry (PIXL) of an olivine cumulate outcrop – Issole – within the Séítah formation. The rock analyzed at Issole is a wehrlite dominated by olivine (Fo46±1) and interstitial phases, including augite, late olivine, spinel, and feldspathic material. Compared to other outcrops from Séítah, Issole is more iron-rich and records substantial alteration processes. We combine mineral chemistry, textural analysis, and thermodynamic modeling to show that Séítah olivines crystallized from a basaltic parent magma, compositionally similar to the most primitive basalts in the Máaz formation. Crystallization of this parent magma produces residual melts that follow the magmatic differentiation trend defined by Máaz basalts. Moreover, the mineral assemblages predicted by our model during crystallization are consistent with observations from Séítah rocks but show some differences in composition. These differences can be reconciled by considering post-cumulus processes that modified the mineral assemblage in Séítah, including FeMg exchange between olivine and pyroxene. Our results indicate that Séítah and Máaz are likely genetically related, and their formation involved both accumulation of crystals at depth and eruption of lavas. The emplacement of Séítah likely occurred as a near-surface, sill-like igneous intrusion into previously erupted Máaz lava flows. The relationship between Séítah and Máaz demonstrates that magmatic differentiation processes, similar to those responsible for the formation of some Martian meteorites, can produce highly diverse lithologies and mineral textures in the Martian crust.

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Acknowledgement

We are grateful to the Mars 2020 Science and Engineering team members who participated in tactical and strategic science operations. J.D.H.M. acknowledges support from a grant from the Fulbright Foundation and the Caltech Center for Comparative Planetary Evolution. This work was partially carried out at the Jet Propulsion Laboratory, California Institute of Technology under prime contract with the National Aeronautics and Space Administration (80NMOO18D0004) – this grant supported authors A.C.A, J.A.H. Y.L., A.H.T, L.W, J.V.B., M.M.T., and M.L.C. J.A.H. was also supported by JPL Subcontract #1529702. S.VB. and A.K were supported by the Mars 2020 Participating Science Program, Grant 80NSSC21K0328. M.E.S. and T.K. were supported by the Canadian Space Agency (CSA) M2020 Participating Scientist Program, grant 21EXPMAPS CSA 2021. The Lunar and Planetary Institute (LPI) is operated by Universities Space Research Association (USRA) under cooperative agreements with the Science Mission Directorate of NASA. We also thank J. Brian Balta and an anonymous reviewer for comments that helped improve the quality of the manuscript, as well as Christina Viviano for editorial handling.

Ethics

During the preparation of this work the author used “Grammarly” in order to improve language and readability. After using this tool, the author reviewed and edited the content as needed and take full responsibility for the content of the publication.

Data Availability

All raw data used in this manuscript are available through the NASA Planetary Data System (PDS), Geosciences Node https://pds-geosciences.wustl.edu/. The software for phase equilibrium calculations (Perple_X) is available for download at https://www.perplex.ethz.ch. Input files, data processing scripts, and all the supporting information for this study will remain unmodified in a Zenodo data repository (Hernández-Montenegro, 2025).

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